Given a symmetrical ionospheric path the link is symmetrical regardless of the antennas. An antenna is is deficient in transmit is equally deficient in receive.

From what I read and have experienced the ionosphere is symmetrical most but not of the time. According to an article I read last year East-West ionospheric paths are the ones that are most likely to be non-symmetrical. The non-symmetry was said to be up to 4 dB.

The ionosphere is not homogeneous. It's anything but the spherical representations in introductory articles. Consider it clouds of plasma, non uniform in density, varying in height by 10s of thousands kilometers, continually changing during the day and night. Travel of EM waves will never diffract from the same path, lots of times there a skew paths. This is a tough topic to condense, lots of info available on the web.

Given a symmetrical ionospheric path the link is symmetrical regardless of the antennas. An antenna is is deficient in transmit is equally deficient in receive.

That is almost never true.

Receiving S/N ratio is a function of antenna directivity, local noise floor, propagated noise, receiver bandwidth, and the effective radiated power of the distant station at your direction, angle, and even the useful polarization for the band and path at that moment. Gain is largely meaningless unless gain is so low the system's internal noise starts to contribute significantly to S/N ratio.

Transmitting effectiveness only deals with absolute antenna gain at the desired angle and polarization, and the transmitter power, assuming bandwidth and audio has no issues hurting intelligibility. Directivity and noise floor at the TX site is meaningless when transmitting.

There are consistent HUGE differences in propagated and local noise floors, and this often causes very noticeable dissimilarities in reciprocity for the same antennas and power.

For example, in daylight my noise floor is nearly S1 on 40 meters. I can hear Europeans on 40 meters almost 24 hours a day in winter. I have no hope of working most of them no matter how much power I run, because it is dark over there and their noise floor is probably 20-30 dB higher than mine.

As sunset approaches, my noise floor on 160 through 40 increases 10-20 dB. My signal into Europe increases more than that, probably 70 dB or more, and their signals increase the same.

Let me do it with typical numbers for two locations with numbers instead of words:

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